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The use of hydraulic transmission skills in the driving drive of construction machinery
Source: Bearing network time: 2013-05-13
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1. Overview The travel drive system is an important component of construction machinery. Compared with the operating system; the travel drive system not only needs to transmit more power; it requires equipment with higher power and longer life; Excellent performance in terms of differential speed, changing the direction of rotation of the output shaft and reverse transmission power. Therefore, what kind of transmission method is used; how to better satisfy the needs of various construction machinery travel drives; it has always been faced by the construction machinery industry. The subject, especially these years; following the rapid development of China's transportation, power and other infrastructure construction; construction and resource development planning continues to expand; construction machinery needs to be greatly enhanced in the market; more facing the operating environment is more severe The demanding situation caused by harsh conditions and more chaotic conditions; further advancement of its walking drive system.
Here, attempts are made to discuss the development of hydraulic drive technology in the construction machinery driving system and its rules from the perspectives of skill composition and functional characteristics.
2, according to the single-skill transmission method, the construction machinery walking system begins with the choice of mechanical transmission and hydraulic mechanical transmission (full hydraulic excavator outside) method. Today; hydraulic and electric drive transmission methods are also found in engineering machinery travel drive equipment; Enough display of scientific skills to carry out the grand promotion of this category.
2.1 Mechanical transmission Pure mechanical transmission engine has a low uniform load factor; therefore, it can only be used for step-variable speed change; and the planning method is limited. However, because it has the advantages of high steady-state transmission power and low production cost; The general-purpose passenger cars with small speed and the range of agricultural tractors with strict economic requirements and stable operation speed still occupy the dominant position.
2. 2 Hydraulic transmission hydraulic transmission replaces the clutch in the mechanical transmission; it has the stepless stepless speed regulation. Its outstanding strength is the output torque-speed characteristic close to the hyperbola; The power shifting mechanical transmission can actively match the load and avoid the overload of the power transmission equipment. The power density of the torque converter is large and the load stress is low; the mass production cost is not advanced, making it widely used in large and medium-sized earthmoving Earth moving machinery, lifting and transport machinery, and high-speed vehicles such as automobiles and tanks. However, its characteristics matching and planning methods are limited; the scale of the torque is smaller than that of the poor. 『.
2.3 Hydraulic drive and mechanical transmission comparison. Hydraulic transmission more simply completes the control of its motion parameters (flow) and dynamic parameters (pressure); and hydraulic transmission has outstanding low-speed load characteristics compared to hydraulic transmission. Because of high transmission power Constant power output control; sufficient power usage; simple system planning; stepless speed regulation of output speed; positive and negative operation; high speed rigidity; outstanding advantages such as simple completion of the measures; hydraulic transmission has been widely used in construction machinery The use of hydraulic engineering can be seen in all engineering machinery; many of them have become the primary transmission and control methods. Extreme load conditioning closed loop; constant speed of engine speed control; constant power combination conditioning variable system Development; the hydraulic drive used in the construction machinery walking system provides a broad prospect for development.
Compared with pure mechanical and hydraulic transmission; the main advantage of hydraulic transmission is its quickness of adjustment and planning flexibility; according to the shape and working conditions of construction machinery; the engine, drive wheel, working organization and other components are separated It is placed in a reasonable position; the engine operates at any dispatching speed; the transmission system can exert a large traction; and the transmission system can still maintain higher power in a wide output speed scale; and can easily obtain each Optimized power transmission characteristics; to be accustomed to the load conditions of various operations. The traveling hydraulic drive equipment with closed oil circuit selected in the high speed moving machinery can steplessly adjust the speed; make the vehicle soft start, agile shifting And the direction of the shift is changed without impact. This function is very valuable for vehicles that need frequent starting and shifting in the operation, often with a trek. But compared with the open circuit; the description of the closed circuit, equipment debugging and protection are all Higher difficulty and skill needs.
With the connection of electronic skills and hydraulic skills; it is very convenient to complete various conditioning and control of the hydraulic system. The introduction of computer control and the use of various types of sensing components; more greatly expand the scale of hydraulic components. The sensor monitors various condition parameters of the engineering vehicle; the computer operates the output to control the command instructions; enables the vehicle to complete the active operation within the entire operation scale; the fuel economy, power, and operation yield of the machine reach the optimal value. Therefore; Hydraulic transmission can make engineering machinery easy to complete intelligent, energy-saving and environmental protection; and this has become the development trend of engineering machinery at that time and in the future.
2.4 Electric drive The electric drive is driven by the internal combustion engine; the electric energy is generated to drive the motor to drive the vehicle to move; the electronic conditioning system is used to regulate the speed and steering of the motor shaft; the speed is large; the input component (generator), Output components (motors) and control equipment can be divided into equipment and other strengths. Electric power transmission was first used in diesel electric boats and diesel locomotives; later on large-tonnage mining trucks and some large construction machinery; Small and medium-sized lifting vehicles such as forklifts and tractors for diesel electric power transmission are presented. However, according to some reasons such as skill and economy, the power components for mobile machinery are far less than those used for fixed equipment; Transmission is only a "future skill" for most walking machines.
3. The analysis of the early years of the composite transmission technology can be seen; the transmission method based on single skill used in the construction machinery travel drive system is simple and reliable; it is suitable for some specific occasions and categories. Most of the practice is in use; these transmission skills are often not isolated; there is a mutual penetration and connection between them; and mechanical transmission links are more or less included in hydraulic, hydraulic and electric transmission equipment; The new mechanical and hydraulic transmission equipment is also equipped with electrical and hydraulic control systems. In other words; the use of targeted composite integration methods; the ability to fully utilize the advantages of various transmission methods; learn from each other; then get the best Inductive benefits. It is worth noting that hydraulic transmission equipment with both conditioning and planning flexibility and high power density plays an important role in the process.
3.1 Hydraulic and mechanical and hydraulic transmission composite
(1) The tandem method series method is the most simple and common compound method; it is a high-efficiency area where a mechanical transmission is arranged between the output end of the hydraulic motor or the hydraulic transmission and the transaxle to expand the speed regulation; It has been widely used in loaders, combined harvesters and certain special vehicles. It is developed by directly shifting the power shifting planetary transmission that can change the transmission ratio during the trek to the drive wheel; Wheel-side hydraulic drive; thus eliminating the drive axle; easier to plan.
(2) The parallel method is generally referred to as “hydraulic mechanical power split transmissionâ€; it can be understood as a transmission system that separates hydraulic and mechanical equipment “in parallel†from the transmission power flow; that is, using multi-degree of freedom planetary difference The speedometer divides the power output of the engine into two hydraulic and mechanical "power flows"; by virtue of the controllability of the hydraulic power flow; the two power flows can be steplessly conditioned to the total output speed when merging from the head. The method links the advantages of the stepless speed regulation function of the hydraulic transmission with the high steady state power of the mechanical transmission; obtaining a variable speed device with both infinitely variable speed function and higher power and wider high efficiency area.
According to its planning; this type of composite transmission equipment can be divided into two categories: the first type is the external split type using the planetary gear differential shunt; the common shunt transmission structure can be divided into input split type and output split type. The basic type; the second type is the internal split type using a hydraulic pump or a differential motion split between the rotor and the motor.
The hydraulic transmission transmission of this composite method developed by Komatsu Corporation of Japan; it has been used in construction machinery such as loaders and bulldozers. The agricultural tractors equipped with Vario type continuously variable transmissions produced by German Fendt tractors; the total sales volume exceeded in 2003. 30000 units.
It can be seen that this new type of transmission equipment has increasingly become a strong competitor for large and medium power hydraulic transmission and power shift transmission.
(3) Time-sharing method A special vehicle with a wide difference between the working speed and the non-working condition; the method of selecting the traditional mechanical transmission for high-speed trekking and additional hydraulic transmission equipment for low-speed operation is very satisfactory. The need for the opposite of working conditions. The mechanical hydraulic time-division-driven method has been widely used in such vehicles; this skill has also been used in vehicles such as aircraft de-icing vehicles and field transplanters that require "åŒåŒ speed" and On the machine.
(4) The method of locating the hydraulic motor directly in the wheel is the auxiliary hydraulic drive device; it can handle the construction machinery and needs to improve the traction function; but it can not select the all-wheel drive method; it is difficult to install The problem of the traditional mechanical transmission equipment. The stepless speed regulation function of the hydraulic transmission enables the drive wheels that are driven by different methods to be harmoniously synchronized; this can also be regarded as a power split transmission in a certain sense: the power of the power machine Distributed to several sets of drive wheels; traction that propels vehicle motion after ground coupling. Currently; many construction machinery manufacturers use this skill for some self-propelled drive capabilities; such as self-propelled graders and shovels Machine engineering machinery.
3.2 The combination of hydraulic and electric drive is due to the development of modern skills; electronic skills have a great advantage in the ability and speed of signal handling; and hydraulic and electric drives have their own characteristics in terms of the characteristics of their respective power components. In addition to the existing "electronic nerve + hydraulic muscle" method; there are many successful examples of the composite transmission of power flow; such as: variable frequency or DC speed motor and high efficiency, low pulsation quantitative hydraulic Variable flow hydraulic oil source composed of pump; electro-hydraulic fulfillment unit composed of electric pump-hydraulic cylinder or low-speed high-torque hydraulic motor with integrated equipment; and drive system of hybrid industrial vehicle.
3. 3 secondary conditioning hydrostatic transmission system secondary conditioning hydrostatic transmission skills is through the conditioning of the hydraulic components to complete the transformation of hydraulic energy and mechanical energy. In general; its completion is based on the pressure coupling system Selecting a constant pressure coincidence method between primary components (pumps) and secondary components (motors); relying on real-time conditioning of motor displacement to balance load torque. Currently; the starting point for research on secondary conditioning hydrostatic transmission skills is to drive The process performs energy recovery and energy de novo use; from the microscopic point of view, the hydrostatic transmission overall planning is rationally equipped and the handling characteristics of the hydrostatic transmission system are improved.
In order to make hydraulic motors and reciprocating hydraulic cylinders that do not have bidirectional stepless variables, they can also operate in the constant pressure network of the secondary conditioning system; presenting a "hydraulic transformer" using secondary conditioning skills; it is similar to a power transformer Used to match the user's different needs for system pressure and flow; then complete the power matching of the hydraulic system.
The secondary conditioning hydrostatic transmission system is compared with the traditional hydrostatic transmission system; its strength is easier to control; it can work in four quadrants; it can recover energy without changing energy mode; store energy; use hydraulic energy storage The acceleration can greatly improve the power; and there is no pressure peak in the system; because the primary component and the secondary component separate the device; the oil source can be supplied to multiple hydraulic power components through one pumping station; the cooling cost is reduced; the manufacturing cost of the device is reduced The system power is high.
The second conditioning hydrostatic transmission is compared with the electric drive; it has the advantages of fast closed loop control, high power density, light weight and small equipment space.
Because the secondary conditioning hydrostatic transmission system has many advantages; it has been widely used in many fields. It has been successfully used in the shipbuilding industry, steel industry, large test bench, vehicle transmission, etc. The running car company has already The secondary conditioning skills are used in the driver drive in the driverless delivery system.
4. Concluding remarks Since the 1990s in the 20th century, construction machinery has entered a new period of development; the extensive use of new skills has enabled new plans and new products to emerge. Following the penetration of microelectronics skills into construction machinery; engineering machinery is becoming increasingly intelligent. And the direction of mechatronics; the need for engineering machinery travel drive equipment is becoming more and more stringent. These years; hydraulic skills are agile; hydraulic components are improving; the use of hydraulic transmission in the construction machinery transmission system is changing with each passing day; The advantages of the transmission are also increasingly evident. Can be trusted; with the close connection between hydraulic skills and microelectronics skills, computer control skills and sensing skills; hydraulic transmission skills will play an increasingly important role in the development of engineering machinery travel drive system Important effect.
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